The invention relates to a method for operating a clothes drying appliance, wherein a moisture content of clothes or laundry is determined by measuring a current running through the clothes. The invention also relates to a clothes drying appliance being adapted to perform the method.
A tumble dryer comprises a rotatable drum to contain clothes. To dry moist clothes, the drum is rotated and heated, e.g. by circulating warm air over the clothes. In many tumble dryers, a desired or target moisture content at the end of a drying process or drying cycle can be selected by a user. To achieve the target moisture content, the tumble dryer monitors the moisture content of the clothes and terminates the drying cycle if the target moisture content has been reached. To monitor the moisture content, some tumble dryers use a current sensor that comprises two electrodes within the drum wherein the electrodes are regularly covered by the clothes. A DC voltage is applied to the electrodes. The value of the resulting current through the clothes is related to the moisture content. The moister the clothes are the greater is the current. The tumble dryer can use this current value to estimate the moisture content and to control the drying cycle accordingly. However, the use of a current sensor has the disadvantage that the electrodes are subject to clothes electrolysis that deteriorates the electrode material and accelerates aging of the electrodes. Further, the current sensor exhibits adverse spatial polarization effects. Also, the computational effort is rather high. And generally there is a desire for a more accurate estimation of the moisture content to achieve better and more consistent drying results.